We have had an implementation of __builtin___clear_cache since the
beginning, but didn't have the cooresponding __clear_cache library
routine implemented. This directly conflicts the GCC manual in a
handful of places, which indicates that __clear_cache should work and
that __builtin_clear_cache should function the same way as __clear_cache
by ethier calling it or inlining the functionality.
This patch simply implements __clear_cache via __builtin___clear_cache.
This should be safe as we always have clear_cache insn so therefor
__builtin___clear_cache will never fall back to calling __clear_cache.
I'm not actually sure that silently implementing clear_cache as a NOP
when there is no ISA defined mechanism for icache synchronization is the
right way to go, but that's really a different discussion.
This was reported as Bug 94136, which is a year old but was categorized
as a documentation bug. I believe that categorization was incorrect:
having an empty __clear_cache library routine is simply incorrect
behavior, the fact that __builtin___clear_cache happens to be
implemented as a libc call on Linux is just a red herring suggesting the
documentation fix to point out the name difference. I view this new
behavior as conforming to the existing documentation: we're just
inlining the __clear_cache implementation, even if that implementation
happens to be a call to a very similar looking libc routine.
gcc/ChangeLog
PR target/94136
* config/riscv/riscv.h (CLEAR_INSN_CACHE): New macro.
---
Passes riscv-linux mulilib with no new failures. OK for trunk and
backports to gcc-11, gcc-12?
Changes since v1 <20210430045646.1508805-1-palmerdabb...@google.com>:
* Extra "_" as per Jim's comment.
---
gcc/config/riscv/riscv.h | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/gcc/config/riscv/riscv.h b/gcc/config/riscv/riscv.h
index acae68ebb2d..bb0dcb651d5 100644
--- a/gcc/config/riscv/riscv.h
+++ b/gcc/config/riscv/riscv.h
@@ -1080,4 +1080,9 @@ extern void riscv_remove_unneeded_save_restore_calls
(void);
#define REGISTER_TARGET_PRAGMAS() riscv_register_pragmas ()
+/* We always have a "clear_cache" insn, which means __builtin__clear_cache will
+ never emit a call to __clear_cache. */
+#undef CLEAR_INSN_CACHE
+#define CLEAR_INSN_CACHE(BEG, END) __builtin___clear_cache((BEG), (END));
+
#endif /* ! GCC_RISCV_H */
--
2.38.0
